The conventional drum brake adjusting mechanism is a screw thread or ratchet arrangement which is positioned in the brake drum between the brake shoes. It may be in a strut near the wheel cylinder, which is also used to operate the parking brake, or it may be between the ends of the shoes opposite the shoe ends acted on by the wheel cylinder. It is exposed to brake lining and road dust as well as to water, dirt, oil and other contaminants. This is particularly the case when the brake is on an automotive vehicle. Some adjusters have been previously built into the drum brake wheel cylinder, submerging the mechanism in brake fluid and sealing it in the brake hydraulic system. Prior drum brake adjusters located within wheel cylinders have been of the incrementally adjusting type. They are prone to overadjustment under excess brake actuating pressure.